Adoption of kernel UEK or UEK2

I'm curious to hear stories about Kernel UEK, either one or two and its
adoption in the industry. Given that Red Hat seems to be consistently
producing great financial results one wonders about the Oracle Linux
footprint in the real world.

For me OL 6.2 and 6.3 have been a blessing: free security updates, new
kernels with interesting features etc. However when it comes to large
organisations and standardisation, the terms change. To be even remotely
able to suggest UEK as a kernel to be rolled out to potentially
thousands of systems vendor support is crucial. I wonder if HP, Dell and
others actively certify UEK. Moving up the stack it requires
certification from the SAN vendors for their multipathing drivers, their
storage management software etc. Once you reach the OS stack it's simple
because you can get support from Oracle.

If those of you on Linux, if you wouldn't mind, let me know your
experience with UEK, why it has been adopted or not, and how it went.